The present apparatus pertains to an automatic gain control circuit for a single sideband receiver. A single sideband signal contains the information from one of the sidebands of an amplitude modulated signal without the carrier and other sideband information. Since the single sideband receiver does not have a carrier reference level to set its AGC, information contained in the sideband must be used to keep a constant audio output level. In conversation, voice levels constantly change in amplitude and it is difficult to control a 100 db range in carrier level and also have natural voice quality without harshness due to the AGC attacking and decaying with every syllable.
In many prior art receivers RF or IF derived AGC signals are utilized to control the gain of the RF and/or IF amplifiers. However, these circuits can be extremely unstable because of the high frequencies utilized and a great amount of care must be utilized in the design and placement of the circuits. In many instances shielding is required to prevent oscillations and unwanted interference.